Good adhesion between vulcanized rubber and reinforcing members (either in the form of continuous filaments, fibers, or sheets) is required to manufacture rubber articles, such as, tires, hoses, moldings, and others. It is especially difficult to adhere reinforcing members to saturated rubber cured with free radical vulcanizing agents. U.S. Pat. No. 3,502,542, issued Mar. 24, 1970, describes the use of N-(carboxyphenyl)maleamic acid as a rubber additive to increase the adhesion of rubber to metals. However, rubber articles often fail by loss of adhesion between the rubber and the reinforcing member. Thus, better adhesion is needed to extend the useful life of rubber articles.